The present invention relates to a multiple ranging apparatus for detecting presence or absence of an object, a direction of the object, a distance to the object or the like at multiple points.
Conventionally, for this type of apparatus, there is a multiple ranging apparatus of an automatic focusing camera as shown in FIG. 19 (see JP 07-104477 B, for example). In FIG. 19, light emitted from a light emitting element 1, which is composed of e.g. a light emitting diode (LED) or a laser diode, is made into a beam for projection by an optical lens 2. When an object exists in a detectable range, the light is reflected at a point O1 (or a point O2) on a surface of the object 3 (or the object 4) located on an axis of projection of the light beam. Then, the light passes through an optical lens 5 for light reception, so that a light spot is formed at a point P1 (or a point P2) on a one-dimensional light receiving element 6 composed of e.g. a one-dimensional PSD (positive Sensitive Diode), where the point 1 (or the point 2) is on an extension of a line connecting the point O1 (or the point O2) and a center point of the optical lens 5 for light reception.
Distances of multiple points are measured with use of a plurality of light emitting elements 1 by applying the conventional distance measuring method for the optical ranging apparatus based on the principle of optical triangulation, as described in (i) and (ii) below.
i) Presence or absence of an object is detected in accordance with the amount of received light on light spots formed on the one-dimensional light receiving element 6.
ii) Distances d1, d2 from a ranging apparatus 7 to the objects 3, 4 are measured with use of change in voltage outputted from the one-dimensional light receiving element 6 according to positions of the light spots.
The conventional multiple ranging apparatus, however, has such a disadvantage as follows. In such a conventional multiple ranging apparatus as shown in FIG. 19, the one-dimensional light receiving element 6 is used as a light receiving element. In this case, when distance measuring for multiple points is simultaneously carried out, it is impossible to identify which light emitting element 1 the light is emitted from, and therefore, to measure distances to two or more points.
Accordingly, in ranging of multiple points, ranging measurements should be carried out at some time intervals in such a manner that timing of the ranging measurements may not coincide. Thus, it takes a considerable length of time to carry out the ranging.